Thomas



T H BURRIDGE STEAM SAFETY VALVE.

Patented Apr. 23, 1867.-

W 'Zizasaes lniteh grates gatmt @ffitje.

THOMAS H. BURRIDGE, OF LOUIS, MISSOURI, ,ASSIGNOR TO HIMSELF AND G. C.FABIAN, OF THE SAME PLACE.

Letters Patent No. 64,070, dated April 23, 1867.

IMPROVEMENT IN STEAM SAFETY-VALVES.

TO ALL VHOM IT MAY CONCERN:

Be it known that I, T. H. BURRIDGE, of St. Louis, in the county of St.Louis, and State of Missouri, have invented certain new and usefulimprovements in Steam Safety-Valves; and I do hereby declare thatthet'ollowing is a full and complete description of the construction andoperation of the same, reference being had to the accompanying drawings,making a part of this specification, in which the drawingis a. view ofthcvalve apparatus. i

A represents a section of a steam boiler, B the seat of the safetywalve,C the valve, D the link by which the valve is attached to the lever E. Fis a supplementary lever, to the free end of whichis attached the weightG. II are standards, to which the levers are pivoted, and I a yoke, bythe means of which the lovers are kept in proper relation to each other.It will be seen that the free end of the lcv'er'E is made to curveupward, thus presenting acurving upper side to the lower side ofthclever F, which is provided with a corresponding curvature. the twofitting into each other, as shown in the drawing. The position of thelevers its thus shown is such as when the valve is at rest or closed. Inthis position the lever F rests upon the lever E at the point X, and atwhich point the weight exerts .the least amount of resistance to thepressure of the steam upon the valve, which, by way of illustration, maybe supposed to be one hundred pounds, which is as much as the boiler isallowed to carry. Now, if thepressure of the steam be raised above onehundred pounds, the valve opens, and as it opens the effectiveresistance of the weight increases by the shifting of the points wherethe two lovers touch; that of the lever E nearer to the free end, andthat of F nearer to the pivoted end, thus multiplying the resistance ofthe weight by changing the relation of thel evers according. to thepressure of the steam above one hundred pounds exerted on the vhlve. Bythis it will be evident tha-t all excess of steam above one hun dredpounds will he allowed to blow off, and the valve immediately closedwhen the extra pressure is reduced, whi h is not the case when theordinary safctywhlve is used, for it will allow thesteam to blow ofi'when below what the boiler may be allowed to carry, for the momentum ofthe steam will not permit the valve to return to its scat until thepressure of steam in the boiler has sunk very much bclow what the boileris allowed to bear, and thus occasion a loss of steam. This defectarises from several causes: first, the valve presents a larger surfaceto the escaping steam when up-aud blowing oil, than when down or closed,hence is required a greater pressure to lift the weight in consequenceof this expansion of the steam by the opening oi the valve; secondly,the lever on rising from its station-l position, moves the weightthrough the arc of a circle, thereby shortening the length of thefulcrum, and, as a conseqiience, more pressure is required to raisetheweight, but the principul reason is the momentum of the steam caused bythe blowing off from the boiler. Liquids and fluids being governed bythe same law, when at rest or confined, there is a dead pressure, moreorless, according to circuun stances; but when allowed t5 escape thereis an increased pressure or power from the velocity on the escaping ol'steam. This additional pressure is sometimes so great on the valve as tothrow the wcightaud lcvcr entirely From their place, and in mostinstances prevents the valve f'romaeturning to its scat until thepressurcis very onuch reduced below that allowed the boi|cr to carry,and thus-causing a large waste of steam. By the application of thisarrangement of'levers this difliculty is avoided, for it' the steam inthe boiler is raised above one hundred pounds to the inch, the lever Fwill be first raised, and in raising will shift ,the fulcrum in bothlevers, and thcrchy efi'ecting an increased value of the weight, whichextra weight will returu the valve to itsseat at one hundred poundsby'following down the steam as it sinks lower; that is, it will notallow the. velocity of the steam to create a momentum above the staticpressure in the boiler of any considerable amount when the valve hasreturned nearly to its seat. 7

Thus it will hc'sccu that 1 increase the value of the weight on thesafety-valve in greater proportiou thau the momentum increases when thesteam lifts the valve This compensating power of the lovers meets andresists the increased pressure on tho.valve occasioned by the momentumo'f'thc steam, for suppose the ordinary safetyvalve to be raised out ofits normal position bypn excess of steam, then ifa little extra weightis added to the lever the valve will rcturuto its statical position longbefore it would if allowed to return without this additional weightbeing applied. The result will be'no loss of steam below what the boileris allowed 'to carry; but without this additional weight the valve willcontinue up by the momentum, and the steam escape until the pfessuxesinks very much below what the boiler will bear, and thus occasion aless of steam. This adaitiorml weight is what this compensating leverwill supply, and thereby prevent a loss of steam in blowing ofl-as-nb'oye said.

What I claim as my improvement, and desil e to secure by Letters Patent,is-

.The Levers E F, constructed and arranged in relation to each other-,and valire, substantially as and for the pu rpose set forth. I I V VTHOMASH. BURRIDGE.

Witnesses WM. REHBERG, AD. V. WEIsE. J

